# Fileset

[Small - 2025 - Kumar - Unconventional Spin Orbit Torques by 2D Multilayered MXenes for Future Nonvolatile Magnetic Memories.pdf](https://mdr.nims.go.jp/filesets/b5a4fa10-c249-4054-b4d1-2380db0da472/download)

## Creator

Prabhat Kumar, [Yoshio Miura](https://orcid.org/0000-0002-5605-5452), Yoshinori Kotani, Akiho Sumiyoshiya, Tetsuya Nakamura, Gaurav K. Shukla, [Shinji Isogami](https://orcid.org/0000-0001-7230-6090)

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Unconventional Spin–Orbit Torques by 2D Multilayered MXenes for Future Nonvolatile Magnetic Memories](https://mdr.nims.go.jp/datasets/a9bcc82c-02bd-42df-8605-8e5abc7e0fb3)

## Fulltext

Unconventional Spin–Orbit Torques by 2D Multilayered MXenes for Future Nonvolatile Magnetic MemoriesRESEARCH ARTICLEwww.small-journal.comUnconventional Spin–Orbit Torques by 2D MultilayeredMXenes for Future Nonvolatile Magnetic MemoriesPrabhat Kumar, Yoshio Miura, Yoshinori Kotani, Akiho Sumiyoshiya, Tetsuya Nakamura,Gaurav K. Shukla, and Shinji Isogami*MXenes have attracted attention in recent years owing to their 2D layeredstructures with various functionalities. To open a new application field forMXenes in the realm of electronic devices, such as ultrahigh-integratedmagnetic memory, a spin–orbit torque (SOT) bilayer structure with MXene ofCr2N is developed: substrate//Cr2N/[Co/Pt]3/MgO using the magnetronsputtering technique. Field-free current-induced magnetization switching inthe bilayer structure is demonstrated, regardless of the charge currentdirections with respect to the mirror symmetry lines of Cr2N crystal. This is aspecific characteristic for the 2D MXene-based SOT-devices. As the SOTefficiency increases with increasing the Cr2N thickness, the first-principlescalculations predict an intrinsic orbital-Hall conductivity with the dominantout-of-plane component, comparing to the spin-Hall conductivity in the Cr2N.X-ray magnetic circular dichroism reveals the out-of-plane uncompensatedmagnetic moment of Cr (mUC.Cr ) in the Cr2N layer at the interface, induced bycontact with the Co in the [Co/Pt]3 ferromagnetic layer. Therefore, the intrinsicbulk orbital-Hall effect in MXene and the interfacial contribution such asspin-filtering-like effect owing to mUC.Cr are considered as possible majormechanisms for the unconventional out-of-plane SOT in the device, ratherthan a crystal symmetry and/or an interlayer exchange coupling.P. Kumar, Y. Miura, G. K. Shukla, S. IsogamiResearch Center for Magnetic and Spintronic MaterialsNational Institute for Materials Science (NIMS)Sengen 1-2-1, Tsukuba, Ibaraki 305-0047, JapanE-mail: isogami.shinji@nims.go.jpY.MiuraFaculty of Electrical Engineering andElectronicsKyoto Institute of TechnologyHashikami-cho,Matsugasaki, Sakyo-ku, Kyoto 606-8585, JapanY. Kotani, A. Sumiyoshiya, T.NakamuraPhotonScience InnovationCenter (PhoSIC)Aoba 468-1, Aramaki-Aza, Aoba, Sendai 980-0845, JapanT.NakamuraInternational Center for SynchrotronRadiation InnovationSmart (SRIS)TohokuUniversity.Aoba 468-1, Aramaki-Aza, Aoba, Sendai 980-8572, JapanThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/smll.202500626© 2025 The Author(s). Small published by Wiley-VCH GmbH. This is anopen access article under the terms of the Creative Commons AttributionLicense, which permits use, distribution and reproduction in anymedium, provided the original work is properly cited.DOI: 10.1002/smll.2025006261. IntroductionThe importance of semiconductor devicesis rapidly increasing owing to the develop-ment of a modern society, in which hu-mans are connected to all types of appli-cations via the Internet. To realize efficientdevices, 2D materials, such as the single-layer graphene and the transition metaldichalcogenides (TMDC), have attractedsignificant attention owing to their variousfunctionalities.[1–9] Furthermore, transitionmetal carbide Ti3C2 with atomic layeredstructures was first discovered in 2011,[10]and has opened a new class of 2D materi-als. It is termed asMXene and is also knownas post-graphene and TMDC.[11] The chem-ical formula is Mn+1XnTx, where the siteM represents the transition metals, suchas Ti and Cr, X represents the 2p light ele-ments C or N, and T represents surface ter-minations such as O and Cl on the outerM layer. Specifically, n varying from 1 to4 corresponds to the number of the sim-plest M─X─M bonding trilayer units ofM2X, while x is a variable. The physicaland chemical properties can be tailored byn, as well as by various combinations of M, X, and T.[12]These characteristics are related to the significant electroneg-ativity of 2p light element X, which allows for the strong or-bital hybridization with the M elements.[13] Thus, MXenes arewidely considered to have immense potential as key materialsfor many device applications. In the past decade, MXenes havecontributed to the fields such as biomedicine,[14] mechanicalscience,[15] optoelectronics,[16] and energy storage.[17] These pi-oneering works inspired our interest in finding more remark-able potential for MXenes. In this study, we aim to develop an-other application field of MXene by expanding it to the field of2D spintronics,[18,19] which has been unfamiliar withMXene, andelucidated its superiority. Furthermore, we examined theMXene-specific spin-transport phenomena beyond charge transport.In the spintronics research, manipulation of themagnetic mo-ment via the spin degree of freedom has attracted considerableattention in terms of electronic devices with low power consump-tion because the spin current, a flow of spin angular momentumwithout electron charge, does not consume power in principle.[20]Specifically, to store the enormous amount of data associatedwith the widespread use of the Internet and mobile applications,Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (1 of 11)http://www.small-journal.commailto:isogami.shinji@nims.go.jphttps://doi.org/10.1002/smll.202500626http://creativecommons.org/licenses/by/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fsmll.202500626&domain=pdf&date_stamp=2025-05-15www.advancedsciencenews.com www.small-journal.comFigure 1. Concept of the field-free CIMS in the 2D MXene-based SOT-device, i.e., the MXene (Cr2N)/ferromagnet bilayer system. The electron-spinsoriented in the out-of-plane direction emerge through the pronounced orbital Hall effect in the MXene layer. The thick green arrows at the interfacerepresent the out-of-plane uncompensated magnetic moment of Cr (mUC.Cr ) induced by the adjacent ferromagnetic layer. ThemUC.Cr can act as a spin-filterthat transfers the polarized electron-spins with the same orientation as themUC.Cr . The out-of-plane oriented spins exert the torque on the ferromagneticlayer, resulting in the magnetic domain switching without in-plane magnetic fields.nonvolatile spin-orbit torque magnetic random access memory(SOT-MRAM) has been extensively studied as one of the stor-age devices that takes advantage of the spin current.[21] Althoughthree types of SOT-MRAMs with the magnetization directions ofthe recording layer in x, y and z have been proposed,[22] the so-called Type-Z with perpendicularly oriented magnetization (in zdirection) has been identified as a promising geometry for fur-ther high-integration and low-power MRAM packages. However,the Type-Z requires an in-plane biasmagnetic field for writing us-ing conventional in-plane current-induced SOT, originating fromthe spin current in conventional heavymetals, such as Ta, Pt, andW. This has been an issue for achieving the miniaturization ofcell size and highly integrated SOT-MRAMs, leading to a recentchallenge for field-free current-induced magnetization switch-ing (CIMS) by SOT, and many approaches have been demon-strated to date:[23] the compositional and/or geometrical gradientin the multilayers;[24,25] the interfacial engineering by nonmag-netic layers;[26,27] the exchange coupling between antiferromag-net/ferromagnet bilayers;[28,29] the crystal symmetricity of non-collinear antiferromagnet and the low-symmetry TMDC;[30–37]and the complex circuit architecture with combined SOT andspin-transfer-torque.[38,39] These are based on the concepts of su-perimposing the out-of-plane SOT component on a conventionalin-plane SOT, which is referred to as an unconventional SOT.In addition to the aforementioned artificial structures and ma-terials, we focus on the 2D bare MXene (M2X) as a spin sourcelayer to realize field-free CIMS. Although there are many can-didates for the M sites, such as Ti, V, W, Mo, and Cr, we em-ployed Cr2N in terms of the phase stability and metallic conduc-tivity, as in the case of conventional transitionmetal nitrides.[40,41]There are three aspects to be focused on for the MXene-basedSOT-device. i) A low-symmetry driven unconventional out-of-plane SOT, similar to the noncollinear antiferromagnets andTMDCs,[30–37] in which field-free CIMS can be induced by an in-plane charge current orthogonal to a mirror symmetry line of thecrystal, but not in parallel. ii) An orbital Hall effect (OHE) in thebulk part of MXene layer. The bilayer system with oxidized lightelements exhibits an unconventional SOTs in spite of their weakspin-orbit interaction (SOI),[42–44] which is discussed based on thetransfer of orbital angular momentum. (iii) An interfacial contri-bution to the out-of-plane SOT. Owing to the advantageous prop-erties of 2D materials, the MXene exhibits an atomically flat in-terface with the ferromagnetic layer, enabling the discernment ofinterfacial effects such as electronic band structure and interlayermagnetic coupling. Recently, van der Waals 2D heterostructuresenable field-free CIMS by the unconventional SOT,[45] which isdiscussed with the interfacial states such as efficient spin trans-parency and interfacial magneto-spin Hall effect.[46] Therefore,we have measured the CIMS with two different directions of in-plane charge current and various thickness of MXene, and wehave quantified polarized spins at an interface via synchrotronradiation in this study.In Figure 1, we depict the possible interpretations of the field-free CIMS in MXene-based SOT-device based on the findingsof this study. Firstly, the spin current in the Cr2N layer is ex-pected to originate from the OHE with out-of-plane component,which dominates the entire SOT exerted on the ferromagneticlayer. Second, the nonmagnetic Cr layer, i.e., the top trilayer-unit of the Cr2N MXene adjacent to the ferromagnetic layer, canbe polarized, resulting in an uncompensated magnetic momentof Cr (mUC.Cr ) in the out-of-plane direction, as depicted by thethick arrows at the interface. This is primarily responsible forthe superposition of the out-of-plane SOT component owing toa spin-filtering-like mechanism at the interface.[27,47] In anotherwords, the spin converted from the orbital angular momentumin the same direction as the mUC.Cr , can be transferred, while thespin in the opposite direction cannot be transferred. This is aunique mechanism for the field-free CIMS in the MXene-basedSmall 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (2 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 2. a1) Unit cell model of the Cr2N bare MXene together with the possible magnetic structure predicted by first-principles calculation. a2) Cross-sectional view and a3) plane view for the 3 × 3 × 1 supercell, where the Cr atoms at the top layer are surrounded by black circles. b1,b2) Out-of-planeXRD profiles for the 20 nm thick Cr–N films deposited with different N2 flow ratio Q = N2/(Ar + N2) while reactive sputtering deposition, and substratetemperature (Tsub). c) Atomic force microscopy image for the 20-nm-thick Cr2N film. d) Magnetization curve measured by the in-plane magnetic field(Hx). e) Anomalous Hall resistance as a function of out-of-plane magnetic field (Hz).SOT-devices, which cannot be explained by the existing scenarioof 2D crystal symmetry.2. Results and DiscussionThe unit cell of Cr2N MXene shows a hexagonal structure witha space group of P3̄1m, as shown in Figure 2a1, and the latticeconstants are a = b = 0.48 nm and c = 0.45 nm. The collinearantiferromagnetic structure has been reported for a wide tem-perature range from 100 K to 500 K,[48–52] which was also pre-dicted by our first-principles calculations, as indicated by the ar-rows on each Cr atom. The cross-sectional and plane views areshown together with their coordinates in Figure 2a2,a3, wherethe Cr atoms in the top layer are surrounded by the black circlesto distinguish them from the bottomCr layer. The top and bottomCr layers exhibited a close-packed structure, and N atoms werepresent at the octahedral sites between the two Cr layers. Notethat the present Cr2N belongs to the family of bare MXene with-out T sites, but the Cr-N-Cr trilayer unit is bonded via stackingof N layers. Figure 2b1 shows the out-of-plane X-ray diffraction(XRD) profiles of pure Cr, CrN, and Cr2N films with a thicknessof ∼20 nm on the c-plane oriented Al2O3 substrate. Each phasecan be formed using different ratios of N2 gas flow, defined as Q= N2/(Ar + N2), in reactive sputtering deposition. At Q = 0%, apure Cr filmwas grownwith (110) texture. ForQ= 5%, the fringeoscillation was observed near the XRD peak at 2𝜃/𝜔 ≈ 40° and88°, suggesting the long-range and stoichiometric Cr2N-MXenephase formationwith hexagonal crystal structure with long-rangeatomically flat interfaces. ForQ= 10%, the CrN, which is anotherphase of the Cr-N intermetallic compound with face-centered-cubic structure, was grown in (111) texture. Figure 2b2 showsthe substrate temperature (Tsub) dependence of the out-of-planeXRD profiles of Cr2N films with the same thicknesses. Althoughthe texture with (0001) orientation can be grown even at roomtemperature (RT), high atomic order was obtained at Tsub rang-ing from 350 °C to 650 °C. Figure 2c shows the atomic force mi-croscope image for the 20-nm-thick Cr2N film to show the longrange flatness. The root mean square roughness was evaluatedto be only 0.12 nm, suggesting the atomically flat surface as in-dicated by the fringe oscillation in Figure 2b1. Figure 2d,e showsthe in-plane magnetic properties (in x-direction) and the anoma-lous Hall measurements with the magnetic field along the out-of-plane direction (in z-direction) of Cr2N layer. The magnetiza-tion was negligible without hysteresis, which can be attributed tothe antiferromagnetism of Cr2N, as predicted by first-principlescalculations.[48–52]To investigate the CIMS characteristics owing to Cr2NMXene, we prepared SOT-devices, as depicted in Figure 3a:substrate//Cr2N(5 nm)/[Co(0.35 nm)/Pt(0.3 nm)]3/MgO(2 nm).The Co/Pt multilayer with three periods, which is described as[Co/Pt]3, provides sufficient perpendicular magnetic anisotropy,resulting in an out-of-plane magnetization (MCo/Pt) at the re-manent state (see Figure S1 in the Supporting Information).Figure 3b1,b2 exhibit (0001) plane of the Cr2N supercell, which isthe same as that shown in Figure 2a3, and mirror symmetry axesare depicted by the blue dashed lines (m). In order to explore thespecific characteristics of Cr2N/ferromagnet system that cannotbe explained by such mirror symmetry, we intentionally applieda charge current pulse parallel and orthogonal to the mirroraxis, in which the out-of-plane SOT vanished for only theSmall 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (3 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 3. a) Measurement configuration of the current-induced magnetization switching (CIMS) and representative stacking structure, where the 5 nmthick MXene layer consists of ∼10 unit-layers of Cr2N. b1,b2) Two different directions of the current pulse with respect to mirror symmetry line (m) in theCIMS demonstration. c1,c2) Anomalous Hall resistance for the same sample with magnetic field along out-of-plane (Hz) and in-plane directions. c3,c4)Representative CIMS with and withoutHx. c5)Hx dependence of JCr2N for the Cr2N growth temperature (Tsub) of 350 °C and 650 °C. c6) Field-free CIMSratio relative to the full switching by Hz for various Tsub. The green and blue symbols represent the same results, but with the insertion of 1 nm thick Ptand Cr layers, respectively, for comparison. The red symbol indicates the result with circular shaped pillar devices. d1,d2) Representative field-free CIMSloops for the pillar device with the current pulses parallel and orthogonal to m (see Figure S5 in the Supporting Information).configuration of parallel (Figure 3b1) in the case ofWTe2/ferromagnet systems.[33,34] The anomalous Hall resis-tance (Rxy) with the magnetic field sweep along the out-of-plane(Hz) and in-plane (Hx) direction is shown in Figure 3c1,c2,respectively, where MCo/Pt is indicated by arrows. The Rxy am-plitude for 𝜇0Hz = 0 was consistent with that for 𝜇0Hx = 0,suggesting sufficient perpendicular magnetic anisotropy inthe [Co/Pt]3 layer such that MCo/Pt points in z-direction at themagnetic remanent state. Figure 3c3 shows the CIMS behav-iors under the bias field of Hx, where the load current pulseduration is 10 ms and the direction is parallel to m (m || I) asdescribed in Figure 3b1. The change in Rxy, corresponding tothe magnetization switching, was remarkably sharp as observedin the conventional heavy-metal based SOT-device with Type-Ygeometry,[53] and the polarity of CIMS loop depending on theHxwas clockwise (CW) for 𝜇0Hx = +29 mT and counter-clockwise(CCW) for 𝜇0Hx = -18 mT. It should be noted that the partialCIMS occurred at 𝜇0Hx = 0 (field free) as shown in Figure 3c4,and the effective critical current density flowing in the Cr2N layer(JCr2N) was ∼30 MA/cm2. Specifically, the value was obtained byeliminating the current shunting to the [Co/Pt]3 layer based onthe measured resistivity of Cr2N and [Co/Pt]3 layers (see FigureS2 in the Supporting Information). Note that the JCr2N obtainedis comparable to that of Type-Y devices,[53] which include heavy-metals with strong SOI and high SOT efficiency. The polarityof the field-free CIMS was CW, which was confirmed for theother 10–20 devices. The JCr2N-Hx diagram shown in Figure 3c5revealed that the JCr2N decreased with increasing Hx, and thefield-free CIMS was achieved even at lower Tsub = 350 °C (seeFigure S3 in the Supporting Information). In the productionline of the CMOS transistor, in which the SOT-MRAMs are to beembedded, post-annealing has been performed at ∼400 °C. Notethat the Cr2N based SOT-devices have enough heat endurance toexhibit a stable CIMS owing to the robustness of the Cr2N crystalstructure with respect to growth temperature (Figure 2b2). Theratio of field-free CIMS to the full CIMS was approximately20%, regardless of Tsub, as shown in Figure 3c6. These interme-diate states were also observed in the other devices as well weSmall 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (4 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 4. a1,a2) Cr2N layer thickness (tCr2N) dependence of the out-of-plane AHE and CIMS loops with the bias field 𝜇0Hx = +29 mT, for the SOT-deviceof substrate//Cr2N(tCr2N)/[Co(0.35 nm)/Pt(0.3 nm)]3/MgO(2 nm). b1,b2) High-field in-plane AHE loops for the first- (1𝜔) and second-harmonic (2𝜔)Hall resistance. The red curve in (b2) represents the fitting result using Equation (2) to distinguish the damping-like (HDL) and field-like (HFL) SOTeffective fields from the magneto thermoelectric effect. c) Damping-like SOT efficiency (𝜉eff) as a function of tCr2N estimated by both the critical JCr2N inCIMS loops (red) and the HDL value in the second-harmonic measurements (blue).measured (see Figure S4 in the Supporting Information). Never-theless, the ratio can be enhanced by the 1-nm-thick Cr insertion(blue symbol), while it is slightly suppressed by the 1-nm-thickPt insertion (green symbol), suggesting a relationship betweenthe interfacial phenomena and out-of-plane SOT component.Given that [Co/Pt]3 ferromagnetic layer of the Hall-cross devicehas a large area with 10 μm × 7 μm, multiple domain structureswould form when CIMS occurs, resulting in an intermediatemagnetic state.[54] On the other hand, Figure 3d1 shows thefield-free CIMS loops for the same SOT-devices with [Co/Pt]3ferromagnetic pillar with ∼7 μm in diameter. Note that the in-plane charge current flowed along the mirror symmetry line, inwhich out-of-plane SOT is not allowed in principle. The switch-ing ratio was much larger than that with Hall-cross geometry(Figure 3c4), leading to ∼94% of full switching amplitude (seeFigure S5 in the Supporting Information). Figure 3d2 shows theCIMS with the in-plane charge current orthogonal to the mirrorline, in which the out-of-plane SOT is allowed in principle. Thefield-free CIMS was also observed with similar switching ratio,suggesting an unconventional out-of-plane SOT that cannot beexplained by the existing symmetry driven out-of-plane SOTmechanism.To assess the possible mechanism of the unconven-tional SOT, the effective efficiency (𝜉eff) was quantifiedfor the Hall-cross devices with various Cr2N thicknesses:substrate//Cr2N(tCr2N)/[Co(0.35 nm)/Pt(0.3 nm)]3/MgO(2 nm).Figure 4a1,a2 show the out-of-plane AHE and CIMS loops,respectively, where the charge current direction was parallelto the mirror symmetry axis (m || I). The amplitude of Rxydecreased with increasing current-shunting into the Cr2N layer;thus, we multiplied the factors to expand the loops for visibility.The amplitudes of AHE and CIMS were comparable for eachtCr2N, and the critical current density of JCr2N decreased withincreasing tCr2N. The 𝜉eff was estimated using the followingequation,[55,56]𝜉eff =(2eℏ)(MstCo∕PtHpJCr2N)(1)where Ms and Hp denote the saturation magnetization of Co/Ptferromagnetic layer and domain wall depinning field that is de-fined as Hc = Hp/cos𝜃, respectively.[55,56] Given that the CIMSin the present Hall-cross structure occurs through the domainnucleation and propagation process, the Hp value is necessaryto estimate 𝜉eff as shown in Equation (1). Hp was determined bymeasuring theHc as a function of the polar angle (𝜃) with respectto the film surface (see Figure S6 in the Supporting Information).Note that the current-shunting into [Co/Pt]3 layer was excludedfrom JCr2N by multiplying the ratio of the sheet resistance of theCr2N layer to the entire sheet resistance. It was revealed that 𝜉effincreased monotonically with increasing tCr2N as shown by thered symbols in Figure 4c. To verify this thickness dependence,we examined 𝜉eff by another method, that is a second-harmonicSOT measurement. Figure 4b1,b2 shows the first- and second-harmonic Hall resistances, respectively, of the sample with tCr2N= 3.6 nm. To distinguish between the damping- and field-like SOTs and various magneto-thermoelectric components,[57]Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (5 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 5. a1–a3) Stacking structures for the XMCD measurement at the synchrotron radiation facility. XMCD spectra for the b) Co L2,3-edge), c) CrL2,3-edge, and d) N K-edge of the samples shown in (a1–a3). e) Element-selective out-of-plane magnetic properties for Co and Cr of the sample (a2).such as the ordinary Nernst effect and anomalous Nernsteffect, we conducted the data fitting using the followingequation,[57]R2𝜔xy =RAHE2HDL||Hx|| −Heffk+ RPHEHFL+Oe||Hx|| + RTH (2)at the high-field regime, as shown in Figure 4b2. RAHE, RPHE,and RTH denote the amplitudes of the anomalous Hall resis-tance, planar-Hall resistance obtained by the magnetization ro-tation on the xy-plane, and the resistance originating from themagneto-thermoelectric effect, respectively. Heffk denotes the ef-fective anisotropy field estimated using Equation (S2) in the Sup-porting Information. HDL and HFL+Oe are the damping-like SOTeffective field and the superposition of the field-like effective fieldand Oersted field, respectively. Using RAHE(PHE) ≈ 2.2 Ω (0.02 Ω)and 𝜇0Heffk ≈ 0.6 T, we obtained 𝜇0HDL ≈ 4.2 mT and 𝜇0HFL+Oe ≈0.30 mT, resulting in 𝜉eff = 𝜇0HDL/JCr2N ≈ 0.66 mT/MA cm−2 fortCr2N = 3.6 nm. Note that RTH corresponds to the offset with re-spect to R2𝜔xy ≈ 0 at high field (≈2 T) (Figure 4b2), suggesting thatthe magneto-thermoelectric effect can be ruled out from the ma-jor origin for CIMS in the present Cr2N/[Co/Pt]3 system. Theseresults demonstrate that 𝜉eff dependence on tCr2N via second-harmonic measurements was in agreement with that obtainedvia CIMS, as shown in Figure 4c. Furthermore, we also evaluatedthe out-of-plane and in-plane SOT via low field second-harmonicHall measurements using the sample with different ferromag-netic layer: substrate//Cr2N(8.8 nm)/CoFeB(1 nm)/MgO(2 nm)Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (6 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comTable 1. Spin magnetic moment (mspin) and orbital magnetic moment (morb) for Co, Cr, and N, which are estimated using the sum rule (see Figure S8in the Supporting Information).[58]Sample [𝜇B/atom] Co mspin /morb Cr mspin /morb N mspin /morb Co (calc)a) mspin/morbPure Co 1.83 /0.17 N.A. N.A. 1.63 / ∼0.1Cr2N/Co 0.99 / 0.73 −0.063 / ∼0 ∼0 / ∼0 N.A.Cr2N/Pt N.A. ∼0 / ∼0 ∼0 / ∼0 N.A.a)The values are referred to ref. [59].(see Figure S7 in the Supporting Information). The out-of-planeand in-plane 𝜇0HDL/JCr2N was ≈0.18 mT/MA cm−2 and 0.039mT/MA cm−2, respectively, indicating the presence of out-of-plane SOT based on the Cr2N.To explore the relationship between the SOT and the inter-face emergphenomena, wemeasured the element-selective mag-netic properties at the Cr2N/ferromagnetic interfaces by meansof X-ray magnetic circular dichroism (XMCD) for three samples(Figure 5a1,a2): (a1) the pure Co for comparison, (a2) Cr2N/Cobilayer, and (a3) Cr2N/Pt bilayer. The XMCD signals are shownin Figure 5b–d, and Table 1 summarizes spin (mspin) and orbital(morb) magnetic moments of Co, Cr, and N, estimated using thesum rule (see Figure S8 in the Supporting Information).[58,59] Theresultant values of pure Co (mspin ≈ 1.83 𝜇B; morb ≈ 0.17 𝜇B)were consistent with the calculation results of mspin ≈ 1.63 𝜇Band morb ≈ 0.1 𝜇B,[60] while those of Cr2N/Co (mspin ≈ 0.99 𝜇B;morb ≈ 0.073 𝜇B) were smaller when compared to the pure Co.On the other hand, Cr in the Cr2N/Co was clearly polarized to bemspin ≈ -0.063 𝜇B as shown in Figure 5c, which are close to thevalues for Cr2O3/Co systems reported.[61] Conversely, mspin(orb)of Cr in Cr2N/Pt was negligible. These results show the pres-ence ofmUC.Cr originating from the imbalance in the antiferromag-netic structure of Cr2N due to the adjacent Co layer, as shown inFigure 1. Regarding N polarization, however, mspin(orb) was neg-ligible, as shown in Table 1 and Figure 5d, while N in the Fe–N system shows a finite mspin(orb).[62] These results confirm theatomic-layered structure of Cr2N, which is terminated by the Cratomic-layer at the Cr2N/Co interface. To provide further insightsinto the mUC.Cr , we measured the element-selective magnetic hys-teresis loops along theHz direction for Co L3-edge and Cr L3-edgeas shown in Figure 5e. Sharp magnetization switching of Co andCr was evident at the sameHz, suggesting that themagnetic easy-axis was aligned in the out-of-plane direction. The switching di-rections were opposite to each other with respect to the magneticfield, indicating antiferromagnetic coupling between Co and Cr,i.e., mUC.Cr points down (up) when the magnetization of Co pointsup (down).Hereafter, we discuss possible unconventional SOT mecha-nisms occurring in the Cr2N/[Co/Pt]3 system based on theoret-ical calculations and control samples. The SOT in a ferromag-netic layer generally originates from the spin current generatednot only at the bulk part of the spin-source layer but also at theinterface; therefore, both cases are considered individually. First,the spin diffusion length of pure Cr (𝜆Crs ) is reported as∼2.1 nm atRT and∼4.5 nm at 4.2 K.[63,64] Assuming 𝜆Cr2Ns ≤ 𝜆Crs , due to highatomic density in Cr2N comparing to the pure Cr,[63] the 𝜉eff is ex-pected to decrease for the thickness tCr2N > 𝜆Cr2Ns , if the spin cur-rent predominantly flows though the Cr2N layer. Given this hy-pothesis is not applicable, as indicated in Figure 4c, it is inferredthat the spin current originating from the conventional spin-Halleffect at the bulk part of the Cr2N layer would be a minor cause.Instead, we must consider the long-range transport property thatgives rise to an enhanced 𝜉eff for thicker tCr2N. Specifically, theOHE,[65] which is reported to emerge in the light elements withweak SOI, has longer orbital diffusion length (𝜆Cro ≈ 6.1 nm) com-paring to the 𝜆Crs .[66] Furthermore, enhanced 𝜉eff by increasing theCr thickness in the Co/Cr system has been reported by anothergroup, which has been explained by the OHE.[66,67] In addition tosuch experimental results, we calculated the intrinsic spin-Hallconductivity (𝜎spin(k)xz ) and orbital-Hall conductivity (𝜎orb(k)xz ) in theCr2N (Figure 6a1,a2) to enable the quantitative comparison be-tween the SHE and OHE contributions in the Cr2N, where x, z,and k = {x, y, z} represent the directions of charge current, spincurrent, and spin/orbital polarization, respectively. Note that wefocused only on the possible spin/orbital current flowing in z-direction, which contributes to CIMS of ferromagnetic layers. Inaddition, other components are summarized in Figure S9 in theSupporting Information. Overall, 𝜎spin(k)xz was one or two orders ofmagnitude smaller than 𝜎orb(k)xz , regardless of k direction. There-fore, the hypothesis of the dominant OHE that drown out fromthe experiments in Figure 4c can be supported by the theoreticalprediction, which is similar to the case of pure Cr: 𝜎spin ≈ -100(ℏ/e)(S cm−1) and 𝜎orb ≈ 8000 (ℏ/e)(S cm−1).[68] Focusing on thek-dependence of OHE, note that we find 𝜎orb(z)xz > 𝜎orb(x)xz > 𝜎orb(y)xzat the Fermi level as shown in Figure 6a2. This implies that theorbital current with z-polarization (k = z) emerges in the bulkpart of Cr2N in principle, which is converted into the spin cur-rent, resulting in the out-of-plane SOT for the field-free CIMS. Toprovide insight into the spin and orbital Hall conductivities, thespin and orbital Berry curvatures are analyzed as shown in FigureS10 in the Supporting Information, together with the orbital pro-jected band dispersion of Cr in Cr2N for the high-symmetry line.It was revealed that the Γ-K symmetry line of the Cr2N MXenedominates the contribution to the spin and orbital Hall conduc-tivity. These characteristics are different from the conventionalheavy metals, for example, high Berry curvature near the X andL points, and near the P point and along the path from H pointcontribute to the significant spin-Hall conductivity of the fcc Pt,and 𝛼-Ta, respectively.[69] The spin Hall conductivity at the FermiEnergy was ∼2200 (ℏ/e)(S cm−1) for the fcc Pt and ∼-142 (ℏ/e)(S cm−1) for the 𝛼-Ta.[69] 𝜎orb(k)xz for the Cr2N MXene was compa-rable to the value for the fcc Pt, while 𝜎spin(k)xz was much smallerthan those for the fcc Pt and the 𝛼-Ta.Next, it is essential to consider the interfacial contributionto the out-of-plane SOT, which can dominantly contribute toSmall 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (7 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 6. a1,a2) Energy dependent spin-Hall conductivity (𝜎spin(k)xz ) and orbital-Hall conductivity (𝜎orb(k)xz ) for the Cr2N, where x, z, and k represent thedirections of charge current, spin current, and spin/orbital polarization, respectively. b1–b3,c1–c3,d1–d3) CIMS results for the controlHall-cross samples,with b1–b3) 1 nm thick Cu layer insertion and parallel charge current to mirror symmetry axis, with c1–c3) Pt underlayer, and d1–d3) with only [Co/Pt]6multilayer.the field-free CIMS. Based on the XMCD results, we identi-fied the mUC.Cr oriented in the out-of-plane direction at the in-terface owing to neighboring Co. Even though the conversionefficiency from orbital to spin might not be strong in Cr2N,as in the case of pure Cr,[66] the spin would be scattered ortransferred depending on the direction of mUC.Cr , which is likelya spin-filtering effect by the mUC.Cr at interface.[27,47,69] Becauseof the antiferromagnetic coupling between the MCo/Pt and themUC.Cr , the polarized spin transferred through the interface is al-ways opposite to the MCo/Pt, resulting in field-free determin-istic CIMS. To validate this, we examined the CIMS proper-ties of the control sample with the 1-nm-thick Cu insertion be-tween the Cr2N layer and the [Co/Pt]3 ferromagnetic multilayer,i.e., substrate//Cr2N(5 nm)/Cu(1 nm)/[Co(0.35 nm)/Pt(0.3 nm)]3/MgO(3 nm) (Figure 6b1). Due toweak SOI and non-magnetismof Cu, which can identify the effect ofmUC.Cr on the observed field-free CIMS. Figure 6b2,b3 shows the representative out-of-planeAHE and the CIMS, respectively, where the charge current direc-tion is parallel to the mirror symmetry (m || I). Note that field-dependent CIMS was observed with the same polarity as themain sample (Figure 2c3), while no field-free CIMS was evidentby the Cu insertion. The result was comparable to the differentconfiguration with the orthogonal charge current to the mirrorsymmetry axis as well (see Figure S11 in the Supporting Infor-mation), which can be attributed to the absence of induced mag-netic moment of Cu. We thus conclude that magnetic momentof Cr induced by the Co at the interface plays an essential rolefor field-free CIMS, which may become a key to elucidate oneof the possible scenarios of the spin-filtering mechanism at theinterface between MXene/ferromagnetic layer.Some reports show that SOT-devices with Co/Pt multilayer ex-hibit CIMS by itself, without non-magnetic spin sources, whichis referred to as self-induced SOT.[70] However, the self-inducedSOT cannot become a major origin for the field-free CIMS in thepresent Cr2N/[Co/Pt]3 due to the following considerations.We ex-amined the CIMS properties of the other control samples by re-placing the Cr2N layer with a Pt layer, as shown in Figure 6c1–c3.Unlike the results for the main Cr2N/[Co/Pt]3, the polarity ofCIMS was reversed: CW (CCW) for negative (positive) Hx, andno field-free CIMS was observed, although the [Co/Pt]3 multi-layer is consistent. This CIMS property is consistent with thatobserved in the conventional SOT-device such as Pt/CoPt bilayersystems, in which y-polarized spin current dominates the CIMSmechanisms.[57] These results suggest that the impact of spinsource layer on SOT is much greater than that of Co/Pt multi-layer itself. Furthermore, we confirmed the absence of field-freeCIMS in the controlled [Co/Pt]6 sample without Cr2N layer asshown in Figure 6d1–d3. We thus infer again that the impact of[Co/Pt]3 for the field-free CIMS is minor, if any.An interlayer exchange interaction owing to the mUC.Cr can-not contribute to the field-free CIMS, in terms of the collinearmagnetic structure of mUC.Cr and Co. It has been reported thatthe field-free CIMS can be observed in an SOT bilayer struc-ture consisting of an antiferromagnetic layer with an in-planeNéel ventor and a perpendicularly magnetized ferromagneticlayer.[28] This is because the magnetic structure of ferromagneticlayer near the interface can be tilted to the in-plane directionthrough the interlayer exchange interaction, resulting in the ef-fective in-plane magnetic field to break the inversion symmetry.Conversely, the Cr2N has collinear antiferromagnetic structureswith out-of-plane Néel ventors (Figure 2a), which couples withperpendicularly magnetized Co/Pt ferromagnetic layer and theresultant magnetic structure cannot break the inversion symme-try. Therefore, field-free CIMS cannot be explained by the mech-anism of interlayer exchange interaction for MXene-based SOT-devices.Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (8 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comIt should be noted that non-centrosymmetric materials, suchas monolayer TMDCs, exert out-of-plane SOTs in the adjacentferromagnetic layer when the charge current flows orthogonalto the mirror axis, in which the sign of the out-of-plane SOT re-verses with the sign of the charge current direction.[33,34,36] Re-cent theoretical study predicts a momentum-independent uni-form spin configuration known as persistent spin texture for theother 2D non-centrosymmetric materials of CdTe and ZnTe,[71]which is expected to realize spintronic devices because of manyadvantages such as robustness against strain, layer thickness,and crystal distortion. In addition, the mechanism of the OHEthat occurs in non-centrosymmetric materials has recently beenexamined as an intrinsic property.[72] All of these are classifiedinto the symmetry-driven intrinsic mechanisms. In contrast tothat, an unconventional out-of-plane SOT can emerge by thecharge current flowing even in the direction parallel to the mir-ror axis, which is the specific characteristics of MXenes that can-not be explained by such the conventional scenario with inver-sion symmetry mentioned above. Therefore, investigation of the2D-MXene/ferromagnet interface could be a key to facilitate thefield-free CIMS in the SOT-device with the 2D-MXene.The 2D-MXene has many advantages in principle, such asthe bottom-up formability by the conventional sputtering, thephase stability, the sustainable light elements, and the processcompatibility with CMOS technology. Furthermore, the charge-current-direction independent unconventional out-of-plane SOTmay lead to a robust field-free CIMS for 2D SOT-MRAMs in thefuture.3. ConclusionWe have reported the first demonstration of CIMS in theSOT-device with the sputter-deposited bare 2D-MXene of Cr2N:substrate/Cr2N/[Co/Pt]3/MgO cap. The specific characteristics ofthe MXene-based SOT-device is the field-free CIMS via a possi-ble out-of-plane unconventional SOT, regardless of the in-planecharge current direction with respect to crystal symmetry ofCr2N, which is likely a robust field-free CIMS by MXene. A crit-ical current density is ∼107 A cm−2, which is comparable to thatof the conventional heavy-metal/ferromagnet systems. The Cr2Nthickness dependence of SOT efficiency indicates the bulk OHEcontribution, and 𝜎orb(z)xz dominates the OHE in Cr2N based onthe first-principles calculations. The XMCD study indicates thatthe Cr of Cr2N is polarized by the adjacent ferromagnetic Co ofCo/Pt multilayer, and the mUC.Cr antiferromagnetically couples tothe magnetic moment of Co. Thus, the field-free CIMS observedin MXene-based SOT-device can be predominantly attributed tothe spin with z -component originating from the bulk OHE andthe spin-filtering-like effect at the interface due to mUC.Cr .4. Experimental SectionFilm Fabrication and Characterization: An Al2O3 crystal substrate witha (0001) plane orientation was cleaned with ethanol and acetone via ul-trasonic cleaning and flash annealed at 650 °C for 30 min in the sputter-ing chamber with a base vacuum pressure of approximately 10−7 Pa. TheCr2N filmwas deposited on the substrate using theDCmagnetron reactivesputtering for the Cr target at Tsub from RT to 650 °C with the gas mixtureof N2/(Ar + N2) = 5%, where the deposition rate was 1.68 nm min−1.The Co/Pt multilayer and MgO capping layer were deposited via DC andRF magnetron sputtering at RT. The crystal structure was investigated viaX-ray diffraction (XRD; SmartLab; Rigaku Corporation) with Cu-K𝛼 radia-tion. The surface roughness is evaluated via atomic force microscopy. Themagnetic properties and anomalous Hall effect were measured at RT us-ing a magnetic property measurement system (MPMS; Quantum DesignInc.) and a physical property measurement system (Dynacool; QuantumDesign Inc.), respectively.Element Selective Magnetic Properties Measured via XMCD: The XMCDmeasurements were performed at the BL14U Synchrotron Radiation Facil-ity, NanoTerasu. Soft X-ray absorption spectra (XAS) were recorded usingthe total electron yield (TEY) method while scanning photon energy at RT.The XMCD signal was obtained by subtracting each XAS signal for circu-larly polarized light with positive and negative helicities. In particular, forCr and N with tiny magnetic moments, the XAS measurement for eachhelicity was repeated five times and averaged to boost the signal-to-noiseratio. The magnetic field was applied perpendicularly to the surface of thesample. Element-selective magnetic properties against the applied field(ESMH) were measured for the L3-edge of Co and Cr at RT.CIMS and Second-Harmonic Measurements: Photolithography and Arion milling were employed to fabricate the measurement devices with Hallcross and pillar patterns, in which the line width of charge current channelis 10 μm and the diameter of pillar is ∼7 μm. A customized system wasused for the CIMS experiments. A rectangular current pulse was appliedto the current channel of the Hall cross devices with durations of 10 msusing a pulse generator (FG420; Yokogawa Electric Co.). The Hall voltagewas recorded using a digital multimeter (7555; Yokogawa Electric Co.) atevery interval between the current pulses, that is, 1 s after the last cur-rent pulse. The DC current to sense the Hall voltage was 0.5 mA (≈0.60MA cm−2) for Hall cross devices, and 0.2 mA (≈0.14 MA cm−2) for pillardevices, which were applied using a DC power source (G210, YokogawaElectric Co.). The sensing current density was approximately 2% of criticalcurrent density, which can be negligibly small for CIMS. Themagnetic fieldfrom the electromagnet was uniform within a gap length of 3 cm and anarea 5 cm in diameter. The device was placed away from the electromagnetfor field-free CIMS to eliminate any residual field from the magnetic polepieces. The second-harmonic Hall voltage was recorded using a lock-inamplifier (LI5640, NF Co.) while the in-plane applied field was scanned. Asinusoidal wave with an effective amplitude of 3 mA (≈4 MA cm−2) andfrequency of 33.123 Hz was applied using a pulse generator (FG420; Yoko-gawa Electric Co.). A common device and sample package were used forCIMS and second-harmonic measurements. All measurements were per-formed at RT.Computational Procedure for Spin/Orbital-Hall Conductivities: First-principles calculations were performed using the Vienna ab initio Sim-ulation Package.[73] Projector-augmented wave (PAW) pseudo-potentialswere used for the atomic potentials of Cr and N with a plane-wave cut-off energy of 500 eV.[74] The generalized gradient approximation for theexchange and correlation energies were adopted, including the spin–orbitinteraction with 10× 10 × 10 k-points in the first Brillouin zone.[75] The on-site Coulomb interactionwas considered,U= 3 eV, for the Cr atom. The lat-tice parameters of Cr2N are the same as those shown in Figure 2a.[76] Thespin-Hall conductivity (𝜎 spin) and orbital-Hall conductivity (𝜎 orb) werecalculated based on linear response theory as:[77,78]𝜎X(𝛾)𝛼𝛽(E) = eV∑kΩX(𝛾)𝛼𝛽(k, E) (3)ΩX(𝛾)𝛼𝛽(k, E) is the orbital Berry curvature provided by:[79]ΩX(𝛾)𝛼𝛽(k, E) = 2 ℏ2m2e∑n>m[fkm (E) − fkn (E)]Im⟨km||||(p̂X(𝛾)𝛼)|||| kn⟩⟨kn |||p̂𝛽 ||| km⟩(𝜀kn − 𝜀km)2(4)where V denotes the unit-cell volume, me denotes the electron mass, mand n denote the occupied and unoccupied band indices, respectively.Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (9 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comp̂X(𝛾)𝛽denotes “spin” or “orbital” current operator (X = spin or orbital),where p̂spin(𝛾)𝛼 = p̂𝛼 ŝ𝛾 + ŝ𝛾 p̂𝛼 and p̂orbital(𝛾)𝛼 = p̂𝛼 L̂𝛾 + L𝛾 p̂𝛼 . Furthermore,p̂𝛼 (p̂𝛽 ) is 𝛼(𝛽)-axis component of the momentum operator, ŝ𝛾 denotesthe spin angular momentum operator with the spin quantum axis along 𝛾direction, and L̂𝛾 denotes the orbital angular momentum operator along𝛾 direction. Additionally, |kn〉 denotes the eigenstate with the eigenenergy𝜖kn, and fkn(E) denotes the occupation function for band n andwave-vectork at the energy (E) relative to the Fermi level (EF). The 𝜎spin(orb) of Cr2Nwas computed using 30 × 30 × 30 k points in the first Brillouin zone.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThe authors thank Dr. Shiratsuchi for the discussion about XMCD re-sults. The XMCDmeasurements were performed at the BL14U of the syn-chrotron radiation facility NanoTerasu. This work was supported by KAK-ENHI Grants-in-Aid No. 23K22803 from the Japan Society for the Promo-tion of Science (JSPS). Part of this work was performed under the Cooper-ative Research Project Program of the RIEC, Tohoku University.Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are available from thecorresponding author upon reasonable request.Keywordsfield-free switching, MRAM, MXene, unconventional SOT, XMCDReceived: February 3, 2025Revised: April 1, 2025Published online:[1] A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V.Grigorieva, A. A. Firsov, K. S. Novoselov, Science 2004, 306, 666.[2] Q. H. Wang, K. Kalantar-Zadeh, A. Kis, J. N. Coleman, M. S. Strano,Nat. Nanotechnol. 2012, 7, 699.[3] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, A. Kis, Nat.Nanotechnol. 2011, 6, 147.[4] H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, A. Javey,NanoLett. 2012, 12, 3788.[5] B. Radisavljevic, M. B. Whitwick, A. Kis, ACS Nano 2011, 12, 9934.[6] A. Pospischil, M. M. Furchi, T. Mueller, Nat. Nanotechnol. 2014, 9,257.[7] A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C.-Y. Chim, G. Galli, F.Wang, Nano Lett. 2010, 10, 1271.[8] Y. Cao, V. Fatemi, S. Fang, K. Watanabe, T. Taniguchi, E. Kaxiras, P.Jarillo-Herrero, Nature 2017, 556, 43.[9] Y. Qi, M. A. Sadi, D. Hu, M. Zheng, Z. Wu, Y. Jiang, Y. P. Chen, Adv.Mater. 2023, 35, 2205714.[10] M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J. Niu, M. Heon, L.Hultman, Y. Gogotsi, M. W. Barsoum, Adv. Mater. 2011, 23, 4248.[11] M. Naguib, V. N. Mochalin, M. W. Barsoum, Y. Gogotsi, Adv. Mater.2014, 26, 992.[12] X. Li, M. Li, Z. Huang, G. Liang, Z. Chen, Q. Yang, Q. Huang, C. Zhi,Energy Environ. Sci. 2021, 14, 407.[13] S. Isogami, Y. K. Takahashi, Adv. Electron. Mater. 2023, 9, 2200515.[14] N. Driscoll, A. G. Richardson, K. Maleski, B. Anasori, O. Adewole, P.Lelyukh, L. Escobedo, D. K. Cullen, T. H. Lucas, Y. Gogotsi, F. Vitale,ACS Nano 2018, 12, 10419.[15] J. Zhang, N. Kong, S. Uzun, A. Levitt, S. Seyedin, P. A. Lynch, S. Qin,M. Han, W. Yang, J. Liu, X. Wang, Y. Gogotsi, J. M. Razal, Adv. Mater.2020, 32, 2001093.[16] S. Ahn, T.-H. Han, K.Maleski, J. Song, Y.-H. Kim,M.-H. Park, H. Zhou,S. Yoo, Y. Gogotsi, T.-W. Lee, Adv. Mater. 2020, 32, 2000919.[17] S. Zhao, X. Meng, K. Zhu, F. Du, G. Chen, Y. Wei, Y. Gogotsi, Y. Gao,Energy Storage Mater. 2017, 8, 42.[18] H. Yang, S. O. Valenzuela, M. Chshiev, S. Couet, B. Dieny, B. Dlubak,A. Fert, K. Garello, M. Jamet, D.-E. Jeong, K. Lee, T. Lee, M.-B. Martin,G. S. Kar, P. Sénéor, H.-J. Shin, S. Roche, Nature 2022, 606, 663.[19] Y. Liu, Q. Shao, ACS Nano 2020, 14, 9389.[20] S. Maekawa, T. Kikkawa, H. Chudo, J. Ieda, E. Saitoh, J. Appl. Phys.2023, 133, 020902.[21] V. D. Nguyen, S. Rao, K. Wostyn, S. Couet, npj Spintronics 2024, 2, 48.[22] S. Fukami, T. Anekawa, C. Zhang, H. Ohno, Nat. Nanotechnol. 2016,11, 621.[23] H. Wu, J. Zhang, B. Cui, S. A. Razavi, X. Che, Q. Pan, D. Wu, G. Yu, X.Han, K. L. Wang,Mater. Futures 2022, 1, 022201.[24] T.-Y. Chen, H.-I Chan, W.-B. Liao, C.-F. Pai, Phys. Rev. Appl. 2018, 10,044038.[25] Z. Zheng, Y. Zhang, V. Lopez-Dominguez, L. Sanchez-Tejerina, J. Shi,X. Feng, L. Chen, Z. Wang, Z. Zhang, K. Zhang, B. Hong, Y. Xu, Y.Zhang, M. Carpentieri, A. Fert, G. Finocchio, W. Zhao, P. K. Amiri,Nat. Commun. 2021, 12, 4555.[26] V. P. Amin, J. Zemen, M. D. Stiles, Phys. Rev. Lett. 2018, 121,136805.[27] G. Choi, J. Ryu, S. Lee, J. Kang, N. Noh, J. M. Yuk, B.-G. Park, Adv.Mater. Int. 2022, 9, 2201317.[28] S. Fukami, C. Zhang, S. DuttaGupta, A. Kurenkov, H. Ohno, Nat.Mater. 2016, 15, 535.[29] Y.-C. Lau, D. Betto, K. Rode, J. M. D. Coey, P. Stamenov, Nat. Nan-otechnol. 2016, 11, 758.[30] Y. You, H. Bai, X. Feng, X. Fan, L. Han, X. Zhou, Y. Zhou, R. Zhang, T.Chen, F. Pan, C. Song, Nat. Commun. 2021, 12, 6524.[31] S. Hu, D.-F. Shao, H. Yang, C. Pan, Z. Fu, M. Tang, Y. Yang, W. Fan, S.Zhou, E. Y. Tsymbal, X. Qiu, Nat. Commun. 2022, 13, 4447.[32] C. Cao, S. Chen, R.-C. Xiao, Z. Zhu, G. Yu, Y. Wang, X. Qiu, L. Liu, T.Zhao, D.-F. Shao, Y. Xu, J. Chen, Q. Zhan, Nat. Commun. 2023, 14,5873.[33] D.Macneill, G.M. Stiehl, M. H. D. Guimaraes, R. A. Buhrman, J. Park,D. C. Ralph, Nat. Phys. 2017, 13, 300.[34] I.-H. Kao, R. Muzzio, H. Zhang, M. Zhu, J. Gobbo, S. Yuan, D. Weber,R. Rao, J. Li, J. H. Edgar, J. E. Goldberger, J. Yan, D. G. Mandrus, J.Hwang, R. Cheng, J. Katoch, S. Singh, Nat. Mater. 2022, 21, 1029.[35] S. N. Kajale, T. Nguyen, N. T. Hung, M. Li, D. Sarkar, Sci. Adv. 2024,10, 8669.[36] X. Wang, H. Wu, R. Qiu, X. huang, J. Zhang, J. long, Y. Yao, Y. Zhao,Z. Zhu, J. Wang, S. Shi, H. Chang, W. Zhao, Cell Rep. Phys. Sci. 2023,4, 101468.[37] I. Shin, W. J. Cho, E.-S. An, S. Park, H.-W. Jeong, S. Jang, W. J. Baek,S. Y. Park, D.-H. Yang, J. H. Seo, G.-Y. Kim, M. N. Ali, S.-Y. Choi,H.-W. Lee, J. S. Kim, S. D. Kim, G.-H. Lee, Adv. Mater. 2022, 34,2101730.[38] E. Grimaldi, V. Krizakova, G. Sala, F. Yasin, S. Couet, G. S. Kar, K.Garello, P. Gambardella, Nat. Nanotechnol. 2020, 15, 111.Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (10 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.com[39] N. Sato, presented at 2020 Symposia on VLSI Technology and Circuits,Honolulu (Virtual), June 2020.[40] S. Khan, A. Mahmood, A. Shah, Q. Raza, M. A. Rasheed, I. Ahmad,Int. J. Miner. Metall. Mater. 2015, 22, 197.[41] M. A. Gharavi, G. Greczynski, F. Eriksson, J. Lu, B. Balke, D.Fournier, A. le Febvrier, C. Pallier, P. Eklund, J. Mater. Sci. 2019, 54,1434.[42] J. Kim, D. Go, H. Tsai, D. Jo, K. Kondou, H.-W. Lee, Y. Otani, Phys. Rev.B. 2021, 103, L020407.[43] S. Ding, A. Ross, D. Go, L. Baldrati, Z. Ren, F. Freimuth, S. Becker, F.Kammerbauer, J. Yang, G. Jakob, Y. Mokrousov, M. Kläui, Phys. Rev.Lett. 2020, 125, 177201.[44] T. An, B. Cui, M. Zhang, F. Liu, S. Cheng, K. Zhang, X. Ren, L. Liu, B.Cheng, C. Jiang, J. Hu, Adv. Mater. 2023, 35, 2300858.[45] Y. Zhang, X. Ren, R. Liu, Z. Chen, X. Wu, J. Pang, W. Wang, G. Lan, K.Watanabe, T. Taniguchi, Y. Shi, G. Yu, Q. Shao, Adv. Mater. 2024, 36,2406464.[46] Y. Dai, J. Xiong, Y. Ge, B. Cheng, L. Wang, P. Wang, Z. Liu, S. Yan, C.Zhang, X. Xu, Y. Shi, S.-W. Cheong, C. Xiao, S. A. Yang, S.-J. Liang, F.Miao, Nat. Commun. 2024, 15, 1129.[47] T. Song, X. Cai, M. W.-Y. Tu, X. Zhang, B. Huang, N. P. Wilson, K.L. Seyler, L. Zhu, T. Taniguchi, K. Watanabe, M. A. McGuire, D. H.Cobden, D. Xiao, W. Yao, X. Xu, Science 2018, 360, 1214.[48] J. D. Browne, P. R. Liddell, R. Street, T. Mills, Phys. Status Solidi A.1970, 1, 715.[49] G. Wang, J. Phys. Chem. C. 2016, 120, 18850.[50] H. Kumar, N. C. Frey, L. Dong, V. B. Shenoy, ACS Nano 2017, 11,7648.[51] S. J. Gutierrez-Ojeda, R. Ponce-Pérez, D. Maldonado-Lopez, D. M.Hoat, J. Guerrero-Sánchez, M. G. Moreno-Armenta, ACS Omega2022, 7, 33884.[52] S. J. Gutierrez-Ojeda, R. Ponce-Pérez, J. Guerrero-Sánchez, M. G.Moreno-Armenta, Graphene 2D Mater. 2024, 9, 47.[53] S. Isogami, Y. Shiokawa, A. Tsumita, E. Komura, Y. Ishitani, K.Hamanaka, T. Taniguchi, S. Mitani, T. Sasaki, M. Hayashi, Sci. Rep.2022, 11, 16676.[54] G. J. Lim, W. L. Gan, W. C. Law, C. Murapaka, W. S. Lew, J. Magn.Magn. Mater. 2020, 514, 167201.[55] O. J. Lee, L. Q. Liu, C. F. Pai, Y. Li, H. W. Tseng, P. G. Gowtham, J. P.Park, D. C. Ralph, R. A. Buhrman, Phys. Rev. B 2014, 89, 024418.[56] X. Qiu, W. Legrand, P. He, Y. Wu, J. Yu, R. Ramaswamy, A. Manchon,H. Yang, Phys. Rev. Lett. 2016, 117, 217206.[57] C. O. Avci, K. Garello, M. Gabureac, A. Ghosh, A. Fuhrer, S. F.Alvarado, P. Gambardella, Phys. Rev. B. 2014, 90, 224427.[58] B. T. Thole, P. Carra, F. Sette, G. van der Laan, Phys. Rev. Lett. 1992,68, 1943.[59] P. Carra, B. T. Thole, M. Altarelli, X. Wang, Phys. Rev. B. 1993, 70, 694.[60] O. Hjortstam, J. Trygg, J. M. Wills, B. Johansson, O. Eriksson, Phys.Rev. B. 1996, 53, 9204.[61] Y. Shiratsuchi, H. Noutomi, H. Oikawa, T. Nakamura, M. Suzuki, T.Fujita, K. Arakawa, Y. Takechi, H. Mori, T. Kinoshita, M. Yamamoto,R. Nakatani, Phys. Rev. Lett. 2012, 109, 077202.[62] C. S. Hanke, R. G. Arrabal, J. E. Prieto, E. Andrzejewska, N. Gordillo,D. O. Boerma, R. Loloee, J. Skuza, R. A. Lukaszew, J. Appl. Phys. 2006,99, 08B709.[63] J. Bass, W. P Pratt Jr, J. Phys.: Condens. Matter. 2007, 19, 183201.[64] D. Qu, S. Y. Huang, C. L. Chien, Phys. Rev. B 2015, 92, 020418(R).[65] B. A. Bernevig, T. L. Hughes, S.-C. Zhang, Phys. Rev. Lett. 2005, 95,066601.[66] S. Lee, M.-G. Kang, D. Go, D. Kim, J.-H. Kang, T. Lee, G.-H. Lee, J.Kang, N. J. Lee, Y. Mokrousov, S. Kim, K.-J. Lee, B.-G. Park, Commun.Phys. 2021, 4, 234.[67] G. Sala, P. Gambardella, Phys. Rev. Res. 2022, 4, 033037.[68] D. Jo, D. Go, H.-W. Lee, Phys. Rev. B. 2018, 98, 214405.[69] V. P. Amin, P. M. Haney, M. D. Stiles, J. Appl. Phys. 2020, 128, 151101.[70] B. Jinnai, C. Zhang, A. Kurenkov, M. Bersweiler, H. Sato, S. Fukami,H. Ohno, Appl. Phys. Lett. 2017, 111, 102402.[71] M. K. Mohanta, P. Jena, Phys. Rev. B. 2023, 108, 085432.[72] S. Bhowal, S. Satpathy, Phys. Rev. B. 2020, 101, 121112(R).[73] G. Kresse, J. Furthmüller, Phys. Rev. B. 1996, 54, 11169.[74] P. E. Blöchl, Phys. Rev. B. 1994, 50, 17953.[75] J. P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 1996, 77, 3865.[76] V. I. Anisimov, J. Zaanen, O. K. Andersen, Phys. Rev. B. 1991, 44, 943.[77] H. Nakano, Prog. Theor. Phys. 1956, 15, 77.[78] R. Kubo, J. Phys. Soc. Jpn. 1957, 12, 570.[79] Y. Miura, K. Masuda, Phys. Rev. Mater. 2021, 5, L101402.Small 2025, 2500626 © 2025 The Author(s). Small published by Wiley-VCH GmbH2500626 (11 of 11) 16136829, 0, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202500626 by Shinji Isogami - National Institute For , Wiley Online Library on [16/05/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.com